LONGSHORE VARIABILITY OF THE COASTAL RESPONSE TOHURRICANES BONNIE AND FLOYD

摘要

Shoreline change resulting from the landfall of Hurricane Bonnie in 1998 and HurricanernFloyd in 1999 was found to be highly variable along a 100-km stretch of coast in southern NorthrnCarolina. Change calculated over a longer, three-year period also showed a large amount ofrnlongshore variability: some sections experienced over 50 m of erosion while other areas were nearlyrnstable. Initial analyses focused on two islands where the mean response and longshore variabilityrnwere strikingly different. Masonboro Island showed a larger magnitude response to Hurricane Floydrnand over the cumulative three-year period than the relatively stable Topsail Island. Masonborornexperienced over 30 m of shoreline erosion over a three-year period while Topsail Island erodedrnonly 8 m (most of which was attributed to Hurricane Bonnie). The longshore variability of shorelinernchange was greater on Masonboro Island and increased over the years studied. The standardrndeviation of shoreline change increased from 6 - 8 m following the hurricanes to 14.5 m over threernyears. The standard deviation of change on Topsail Island was ~6.7 m for each signal, indicatingrnless longshore variability than on Masonboro Island. Shoreline change on Masonboro wasrndominated by a trend that revealed more erosion occurring along the southern end of the island.rnWhen the trend was removed from the signal, most of the remaining variance was contained atrnlength scales shorter than 500 m. On Topsail, most of the variance of the shoreline change signalrnwas contained at long wavelengths (> 2 km); however, only a small percentage of the variance wasrncontained in a trend.